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Book chapter2012Peer reviewed

Limiting nutrient and eutrophication in aquatic systems - the nitrogen/phosphorus dilemma

Håkanson, L.

Abstract

Remedial methods to lower eutrophication should not focus on nitrogen, but on phosphorus, because there are many major uncertainties related to (a) the quantification of atmospheric N2-fixation by cyanobacteria, (b) wet and dry deposition of nitrogen, (c) the algorithm regulating the particulate fraction for nitrogen and hence also (d) sedimentation of particulate nitrogen and (e) denitrification. Occasional very high concentrations of cyanobacteria may may be quantitatively explained by high total phosphorus (TP) concentrations, high temperatures (higher than 15 °C) and/or low TN:TP ratios (lower than 15 by weight). So, there are no general validated mass-balance models for nitrogen which have been tested for independent coastal systems and been demonstrated to yield good predictive power for N only for P. Any N-model can be tuned, using different calibration constant sets for different systems, to give perfect descriptive power, but such tuning may obscure the true aspects of how natural systems work, just like a deodorant covers a bad smell. Because plankton cells include both nitrogen and phosphorus (given by the standard composition C106N16P), because both nutrients are transported to water systems by the same rivers, and because there is in many systems a potential for phosphorus-driven atmospheric N2 fixation by cyanobacteria, one generally finds a marked co-variation between P- and Nconcentrations in aquatic systems. Primary production (e.g., in g C per m3 per day) cannot be predicted from concentrations (e.g., in mg per m3) of dissolved nutrients, such as DIN (dissolved inorganic nitrogen), DIP, phosphate, nitrate or ammonia which are frequently below detection and have very high coefficients of variation (CV), but can only be predicted well from total concentrations of nutrients (TN or TP), i.e., from the total pools of the nutrients in the system. © 2012 by Nova Science Publishers, Inc. All rights reserved.

Published in

Title: Phosphorus : Properties, Health Effects and the Environment
Publisher: Nova Science Publishers

SLU Authors

UKÄ Subject classification

Ecology

Publication identifier

  • ISBN: 978-1-62081-399-7
  • eISBN: 978-1-62081-417-8

Permanent link to this page (URI)

https://res.slu.se/id/publ/132200